L-carnitine is a naturally occurring amino acid derivative that plays a vital role in energy production. Often taken as a supplement, it's touted for its potential benefits in weight loss, brain function, and exercise performance. This article delves into the science behind L-carnitine, exploring its various forms, benefits, optimal dosages, and potential side effects, particularly focusing on its use for weight loss.
What is L-Carnitine?
L-carnitine is a non-essential amino-acid-like compound produced naturally in the body from the amino acids lysine and methionine. It can also be obtained through dietary sources, primarily red meat and dairy products, with smaller amounts found in plant-based foods like avocado and soybeans. Vitamin C is essential for the body to produce L-carnitine in sufficient amounts. More than 95% of the body’s L-carnitine stores are found in skeletal muscle, with trace amounts in the liver, blood, heart, and kidneys.
Vegans and vegetarians, who restrict or avoid animal products, often have lower L-carnitine levels and may benefit from supplementation. Older adults and individuals with certain chronic conditions like cirrhosis and kidney disease may also be at a higher risk of L-carnitine deficiency.
How L-Carnitine Works in the Body
L-carnitine's primary function is to transport long-chain fatty acids into the mitochondria, the "engines" of cells, where these fats are burned to produce energy through a process known as fat oxidation. By facilitating the movement of fatty acids into the mitochondria, L-carnitine helps the body utilize fat as a fuel source. This is why it is often used as a weight loss supplement. L-carnitine enhances the transportation of long-chain fatty acids into the mitochondria of muscle cells and increases fuel availability during low-moderate intensity exercise.
Potential Benefits of L-Carnitine
L-carnitine may offer several health benefits, including:
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- Weight Loss: L-carnitine helps move more fatty acids into your cells to be burned for energy, so it’s sometimes used as a weight loss supplement. It has been theorized that L-carnitine could help your body to produce energy by utilizing the body’s fat stores, allowing you to work out for longer and ultimately aiding in fat loss. Evidence suggests it may promote weight loss by increasing calorie expenditure. Taking an L-Carnitine supplement daily has been proven to increase the blood and muscular concentrations of this amino acid-like compound, which could enhance fat metabolism as a result with increased muscle carnitine concentrations. A 2021 review in 1,239 people with type 2 diabetes also found that taking 2 grams (g) of L-carnitine daily for at least 2 weeks helped promote weight loss. A 2022 study focusing on the potential benefits of carnitine in women with PCOS (Polycystic Ovary Syndrome) showed that supplementation may aid in reducing body weight, BMI, and waist circumference. Additionally, a significant benefit was observed in their lipid profile.
- Improved Exercise Performance and Recovery: By optimizing how the body uses fat for fuel, L-carnitine may allow individuals to exercise for longer periods. Some research suggests that L-carnitine supplementation can reduce muscle damage from high-intensity exercise and play an important role in recovery from strenuous exercise. Supplementing with L-carnitine could also play an important role in recovery from strenuous exercise, with suggested doses of 2-4g daily to optimise results. There’s initial evidence that this could lead to a reduction in various markers of metabolic stress and muscle soreness which is replicated in many studies. However, research is still limited and further studies are needed.
- Enhanced Brain Function: Some research suggests that acetyl-L-carnitine (ALCAR), a specific form of L-carnitine, may help prevent age-related mental decline and improve markers of learning. A 2018 study found that taking 1,500 milligrams (mg) of ALCAR daily for 28 weeks significantly improved brain function in people with dementia. Acetyl-L-carnitine helps in improving cognitive performance and memory as well as enhancing focus.
- Support for Heart Health: L-carnitine may boost energy levels as it increases the amount of fuel availability that the heart requires to function. Research supports medically supervised use of L-carnitine for treating cardiac related issues and is often given by IV by a medical professional. In a systematic review by the Mayo Clinic, carnitine was associated with a 27% reduction in all-cause mortality. L-carnitine may also play a role in keeping cholesterol levels in a healthy range.
- Blood Sugar Regulation: L-carnitine may be beneficial for people with type 2 diabetes. A 2023 review concluded that L-carnitine supplementation may reduce fasting blood sugar and hemoglobin A1c, while also improving insulin sensitivity in people with diabetes, overweight, or obesity. L-carnitine increases fat burning in mitochondria, a process which in turn decreases reliance on the glucose stores of the body. L-Carnitine is also known to increase insulin sensitivity, and it is thus a useful supplement for those suffering from type 2 diabetes. Studies have shown that supplemental L-Carnitine aids in reducing the blood sugar concentration by improving sensitivity to insulin.
- Improved Sperm Quality: L-carnitine is conducive to enhancing sperm health as well as the count and motility of sperm. It could improve the health of reproduction and help men conceive successfully, especially for those whose fertility is failing. Another main L-Carnitine use is enhancing sperm quality and motility, which in turn improves male fertility.
- Potential Role in Treating Depression: In a 2018 review, acetyl-L-carnitine significantly reduced symptoms of depression compared with placebo. Several studies included in this review also found that acetyl-L-carnitine was as effective as antidepressant medications but caused fewer adverse effects. Still, more research is needed to understand how L-carnitine may affect depression.
Types of L-Carnitine Supplements
Different forms of L-carnitine exist, each with specific uses and absorption rates:
- L-Carnitine Tartrate: This form is commonly found in sports nutrition supplements due to its rapid absorption rate. L-carnitine tartrate is found in its highest levels in tissues that use fatty acids as the main fuel source, such as the skeletal and cardiac muscles. L-carnitine tartrate has a rapid absorption rate and helps with fatty acid metabolism.
- Acetyl-L-Carnitine (ALCAR): ALCAR has an acetyl group attached to the carnitine molecule, allowing it to cross the blood-brain barrier more easily. This makes it the most bioavailable form, often used for cognitive enhancement. Acetyl L-carnitine has an acetyl group attached to the carnitine making it more bioavailable and easier to absorb. Acetyl-L-carnitine has all of the benefits of regular L-carnitine, such as improved metabolism, but it more easily crosses the blood-brain barrier.
- Propionyl-L-Carnitine: This form may help improve blood flow in individuals with high blood pressure or related health conditions. Propionyl-L-carnitine: This form of L-carnitine is best for vascular and circulatory health because it promotes nitric oxide production in the body.
- D-Carnitine: This form should not be taken as a supplement.
L-Carnitine Dosage for Weight Loss and Other Benefits
Studies have used a wide range of doses for L-carnitine supplementation. Dosage varies from study to study and may vary depending on the form of carnitine you take. It's crucial to consult with a healthcare professional to determine the appropriate dosage based on individual needs and health conditions.
General dosage guidelines for different forms of L-carnitine are:
- Acetyl-L-Carnitine: 600-2,500 mg per day. Doses vary from 500 to 3,000 mg per day. This form is often used for brain health and function.
- L-Carnitine L-Tartrate: 1,000-4,000 mg per day. Doses vary from 1,000 to 4,500 mg per day. This form is most effective for exercise performance.
- Propionyl-L-Carnitine: 1,000-4,000 mg per day. A 2005 study used a dose of 2 g per day. This form may help improve blood flow in those with high blood pressure or related health conditions.
When using L-carnitine to optimize energy during workouts, it's best to take it about one hour prior to exercise. However, for recovery and weight loss support, taking it after exercise may also be effective. Some experts recommend splitting the daily intake into two or three doses.
Food Sources of L-Carnitine
L-carnitine can be obtained from dietary sources, primarily animal products:
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- Beef: 139 to 143 mg per 3.5 ounces (oz), or 100 g
- Pork: 25 to 61 mg per 3.5 oz (100 g)
- Chicken: 13 to 34 mg per 3.5 oz (100 g)
- Cow’s milk: 40 mg per 3.5 oz (100 g)
- Hard cheese: 3 mg per 3.5 oz (100 g)
Food sources of L-carnitine have a greater absorption rate than supplements. According to a 2004 study, 57% to 84% of L-carnitine is absorbed when consumed from food, compared to only 14% to 18% when taken as a supplement.
Potential Side Effects and Precautions
L-carnitine supplements are generally considered safe for most people when taken as directed. For most people, taking 2 g or less per day is relatively safe and free from any serious side effects. However, some mild side effects are possible, including:
- Heartburn
- Indigestion
- Nausea
- Stomach cramps
- Diarrhea
- A "fishy" odor in urine or breath
Some research has used doses of up to 4,500 mg per day. However, it's important to note that L-carnitine supplements may raise blood levels of trimethylamine-N-oxide (TMAO) over time. High levels of TMAO are linked to an increased risk of atherosclerosis, a disease that clogs the arteries.
Precautions:
- Consult a Healthcare Professional: Before taking L-carnitine, especially if you have existing medical conditions, are pregnant or breastfeeding, or are taking other medications, consult with a doctor or qualified healthcare professional.
- Drug Interactions: L-carnitine may interact with certain antibiotics and anticonvulsants.
- Kidney Disease: Individuals with kidney disease should exercise caution and consult with their doctor before taking L-carnitine supplements.
- Quality Supplements: Choose L-carnitine supplements from reputable manufacturers with good quality control measures.
- Timing: Consume L-Carnitine before exercise for best workout energy and fat burning.
L-Carnitine: Fact vs. Fiction
While L-carnitine shows promise in various areas, it's essential to separate fact from fiction:
- L-Carnitine is not a magic bullet for weight loss: While it can aid in fat metabolism, it's most effective when combined with a healthy diet and regular exercise.
- More is not always better: Taking more than the recommended dose does not necessarily accelerate results and may increase the risk of side effects.
- Individual results may vary: The effectiveness of L-carnitine supplementation can vary depending on individual factors, such as genetics, diet, and exercise habits.
- L-Carnitine is not a replacement for exercise: While L-Carnitine promotes fat metabolism and can improve performance during exercise, it is best utilized when one exercises regularly. The use of L-Carnitine supplement without a proper exercise routine will not be helpful in the long run.